Magnetic recording medium and magnetic recording and reproducing apparatus

ABSTRACT

In a discrete track medium and a patterned medium, a meniscus adsorptive force is reduced and writing into adjacent tracks is prevented. A magnetic layer in lands or patterns in the discrete track medium or the patterned medium is formed into a cylindrical shelly or spherical shelly shape with a uniform thickness. Moreover, a height of cylindrical shelly land or a height of spherical shelly land is changed between 5 nm and 30 nm according to radial positions. Thus, an effect is achieved for providing a magnetic recording medium and a magnetic disk apparatus which are excellent in realizing higher recording density and higher reliability.

CLAIM OF PRIORITY

The present application claims priority from Japanese application JP2006-229709 filed on Aug. 25, 2006, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetic recording medium and amagnetic recording and reproducing apparatus, and more particularlyrelates to a magnetic recording and reproducing apparatus excellent inachieving higher recording density and higher reliability.

2. Description of the Related Art

A magnetic disk apparatus used as an external storage unit for alarge-sized computer or a personal computer system has been demanded toincrease a recording capacity (areal density) per disk. In order toachieve a higher recording density, it will be required in the future toreduce a magnetic spacing from a reader and writer in a magnetic head toa magnetic layer and to improve recording and reproduction performance,positioning accuracy, and reproduction signal processing performancewith respect to the magnetic head and a magnetic recording medium.Particularly, since magnetic field strength is in inverse proportion tothe magnetic spacing squared, the areal density is significantlyincreased when the magnetic spacing is reduced. The magnetic spacing isexpressed as a sum of a flying height at a position of the reader andwriter in the magnetic head stably flying above a surface of themagnetic recording medium on the basis of principles of air filmlubrication, a dent caused by a difference in a processing amount of amagneto-resistive sensor exposed part in a magneto-resistance effecttype magnetic head, a slider overcoat thickness, a medium lubricationfilm thickness and a medium overcoat thickness. The magnetic spacing isreduced by reducing values of those described above. When the flyingheight at the position of the reader and writer in the magnetic head isreduced to several nm, the following problems occur. Specifically, theslider is likely to intermittently come into contact with roughprotrusions on a disk surface. Moreover, when the protrusions arereduced in size to smooth the disk surface, contact vibration is causedby a meniscus adsorptive force of the lubrication film.

In recent years, a discrete track magnetic recording system and a bitpatterned magnetic recording system have been proposed as innovativetechnologies to respond to the higher recording density of the magneticdisk apparatus. These are technologies that allow higher track densityand higher recording density by forming grooves between recording tracksin a magnetic recording medium or by isolating bits to reduce magneticinterference between the adjacent tracks or the bits. In a magneticrecording medium described in Japanese Patent Application Laid-OpenPublication No. 2005-108335, a film surface on a cross-section passing acenter of a ferromagnetic dot of a carbon film that is a medium overcoathas a smooth shape which is gradually reduced toward outside from thecenter. Specifically, a thickness of the carbon film is not uniform andthere is film thickness distribution. Moreover, a thickness of a centerportion passing the center of the ferromagnetic dot is 5 nm, and thethickness of the carbon film at a position of 1/10 of a radius of theferromagnetic dot from an end portion is 3.5 μm. The carbon film havingsuch a cross-sectional shape is formed by performing etching in which anion incident angle is gradually changed from a substrate perpendiculardirection to a longitudinal direction. In an information recordingmedium described in Japanese Patent Application Laid-Open PublicationNo. 2005-276325, a non-magnetic material is buried in respective concaveportions of a magnetic layer formed into a predetermined concave-convexpattern, and a non-magnetic layer is formed on respective convexportions of the magnetic layer. Moreover, an upper center of each of theconvex portions of the magnetic layer is formed into an angular shapegradually protruding upward. A protrusion amount thereof is 1 nm. Such ashape is formed by setting a long ion beam etching time for thenon-magnetic layer. A nanostructure described in Japanese PatentApplication Laid-Open Publication No. 2005-52956 includes a firstcolumnar member and a second member formed so as to surround the firstmember. The second member contains two kinds or more of materials thatcan form eutectic crystal. Moreover, one of the materials is asemiconductor material, a height of the first member from a substrate ishigher than that of the second member from the substrate, and aprotrusion of the first member has a conical shape.

SUMMARY OF THE INVENTION

In the conventional magnetic recording medium, as a factor that inhibitsreduction in the flying height, slider vibration is caused by increasesin a meniscus adsorptive force of a lubricant and a frictional force atthe time of contact with a smooth medium surface, a discrete trackmedium and a patterned medium. Moreover, in innermost and outermostregions where the absolute value of a yaw angle is increased, magneticfluxes are more easily leaked since the writer comes closer to theadjacent track as compared with a middle region where the yaw angle is0°. Moreover, in a conventional discrete track medium, when acylindrical land shape and a flying height hf at a position of a readerand writer are set the same, the cylindrical land shape is formed bydistributing a carbon film that is a medium overcoat. Thus, a magneticspacing is increased. As a result, areal density cannot be increased.

It is an object of the present invention to provide a magnetic recordingmedium which satisfies higher recording density and reduction in aflying height at the same time by reducing a meniscus adsorptive forceas a factor that inhibits reduction in the flying height and bypreventing writing into adjacent tracks also in innermost and outermostregions where the absolute value of a yaw angle is increased. Moreover,it is also the object of the present invention to provide a magneticdisk apparatus including the magnetic recording medium.

The above object is achieved by forming a magnetic layer in lands orpatterns in a discrete track medium or a patterned medium into acylindrical shelly or spherical shelly shape with a uniform thicknessand by changing a height of cylindrical shelly land or a height ofspherical shelly land between 5 nm and 30 nm according to radialpositions of a disk.

According to the present invention, it is possible to realize themagnetic recording medium which satisfies higher recording density andreduction in the flying height at the same time and the magnetic diskapparatus including the magnetic recording medium.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a magnetic recordingmedium according to Embodiment 1 of the present invention.

FIG. 2 is a schematic perspective view of the magnetic recording mediumaccording to Embodiment 1 of the present invention.

FIG. 3 is a schematic cross-sectional view of a magnetic recordingmedium according to Embodiment 2 of the present invention.

FIG. 4 is a schematic perspective view of the magnetic recording mediumaccording to Embodiment 2 of the present invention.

FIG. 5 is a schematic cross-sectional view of a magnetic recordingmedium according to Embodiment 3 of the present invention.

FIG. 6 is a schematic cross-sectional view of a magnetic recordingmedium according to Embodiment 4 of the present invention.

FIG. 7 is a schematic cross-sectional view of a magnetic recordingmedium according to Embodiment 5 of the present invention.

FIG. 8 is a schematic view of a magnetic recording medium according toEmbodiment 6 of the present invention.

FIG. 9 is a schematic view of magnetic flux vectors when a magneticfield is applied to a conventional discrete track medium on its middleperipheral area with a yaw angle of 0° by a writer.

FIG. 10 is a schematic view of magnetic flux vectors when a magneticfield is applied by the writer to the conventional discrete track mediumon its innermost and outermost where the absolute value of the yaw angleis increased.

FIGS. 11A and 11B are views showing a distance between a magnetic layerof the conventional medium and the writer as well as a distance betweena magnetic layer of the medium of the present invention and the writer,respectively.

FIG. 12 is a schematic view showing a configuration of a magnetic head.

FIG. 13 is a schematic view showing the configuration of the magnetichead.

FIGS. 14A and 14B are views showing the distance between the magneticlayer of the conventional medium and the writer as well as a distancebetween a magnetic layer of the medium of the present invention and thewriter, respectively.

FIGS. 15A to 15C are views comparing a flying height of the conventionalmedium with that of the medium of the present invention.

FIGS. 16A and 16B are cross-sectional views when the medium of thepresent invention and the conventional medium come into contact with amagnetic head slider, respectively.

FIGS. 17A and 17B are graphs showing calculation results onrelationships between a meniscus adsorptive force and a curvature ofcylindrical shelly land as well as between the meniscus adsorptive forceand a height of cylindrical shelly land.

FIGS. 18A and 18B are graphs showing calculation results onrelationships between a meniscus adsorptive force and a curvature ofspherical shelly land as well as between the meniscus adsorptive forceand a height of spherical shelly land.

FIGS. 19A to 19F are explanatory views of a method for manufacturing themagnetic recording medium of the present invention.

FIGS. 20A to 20D are explanatory views of another method formanufacturing the magnetic recording medium of the present invention.

FIGS. 21A to 21H are explanatory views of another method formanufacturing the magnetic recording medium of the present invention.

FIGS. 22A to 22F are explanatory views of another method formanufacturing the magnetic recording medium of the present invention.

FIGS. 23A to 23E are explanatory views of a method for manufacturing amold of the magnetic recording medium of the present invention.

FIGS. 24A to 24I are explanatory views of a method for manufacturing themagnetic recording medium of the present invention.

FIGS. 25A to 25C are explanatory views of a method for manufacturing themagnetic recording medium of the present invention.

FIG. 26 is an explanatory view of a range of use of the magneticrecording media according to Embodiments 4 and 5 of the presentinvention.

FIGS. 27A and 27B are schematic views of a magnetic disk apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the drawings, embodiments of the present inventionwill be described below.

FIG. 1 is a schematic cross-sectional view of a magnetic recordingmedium according to Embodiment 1 of the present invention, and FIG. 2 isa schematic perspective view thereof. A magnetic recording medium 1 ofthis embodiment is a discrete track medium which has grooves 11 andlands 12 and has tracks formed by the lands 12. Each of the lands 12 hasan overcoat 111, a magnetic layer 112, an underlayer 113 such as SiO₂,an underlayer 1113 such as a soft magnetic underlayer, and anon-magnetic substrate 114. A lubricant 1111 is applied onto a surfaceof the overcoat 111. The magnetic layer 112 is formed to have a curvedshape of which height is higher in its center portion than in its endportion in a state where a film thickness thereof is fixed. As shown inFIG. 1, a length between the center portion of the magnetic layer 112and the end portions thereof in a track width direction is defined as aheight of cylindrical shelly land. FIG. 2 shows a dimensional example. Awidth Gwc of the groove 11 is 100 nm, a depth Gdc of the groove is 75nm, a width Lwc of the land 12 is 100 nm, and a track width Tp that is adistance between adjacent lands is about 200 nm. The height δc ofcylindrical shelly land of the land 12 is about 5 nm, and a curvature Rcof cylindrical shelly land is about 505 nm. The curvature Rc ofcylindrical shelly land is expressed as follows by use of the land widthLwc and the height of cylindrical shelly land.

Rc=((Lwc/2)²+δ²)/(2δc)

FIG. 3 is a schematic cross-sectional view of a magnetic recordingmedium according to Embodiment 2 of the present invention, and FIG. 4 isa schematic perspective view thereof. A magnetic recording medium 2 ofthis embodiment is a patterned medium which has grooves 21 and patterns22 and has respective recording bits formed by the patterns. Each of thepatterns 22 has an overcoat 111, a magnetic layer 112, an underlayer 113such as SiO₂, an underlayer 1113 such as a soft magnetic underlayer, anda non-magnetic substrate 114. A lubricant 1111 is applied onto a surfaceof the overcoat 111. The magnetic layer 112 is formed to have aspherical shape in a state where a film thickness thereof is fixed. Asshown in FIG. 3, a length between a center portion of the magnetic layer112 and side end portions thereof is defined as a height of sphericalshelly land. FIG. 4 shows a dimensional example. A width Gw of thegroove 21 is 100 nm, a depth Gd of the groove is 75 μm, a width Lw ofthe pattern 22 is 100 nm, and a track width Tp and a bit width Tpp, eachof which is a distance between adjacent patterns, are about 200 nm. Theheight δ of spherical shelly land of the pattern 22 is 5 μm, and acurvature R of spherical shelly land is about 505 nm. The curvature R ofspherical shelly land is expressed as follows by use of the width Lw ofthe pattern 22 and the height δ of spherical shelly land.

R=((Lw/2)²+6²)/(2δ)

FIG. 5 is a schematic cross-sectional view of a magnetic recordingmedium according to Embodiment 3 of the present invention. A magneticrecording medium 1 or 2 of this embodiment has grooves 11 and lands 12or has grooves 21 and patterns 22. The lands 12 or the patterns 22 areformed of an overcoat 111, a magnetic layer 112, an underlayer 113 suchas SiO₂, an underlayer 1113 such as a soft magnetic underlayer, and anon-magnetic substrate 114. The grooves 11 or the grooves 21 are formedof the overcoat 111, a non-magnetic material 118, the magnetic layer112, and the underlayer 1113 such as the soft magnetic underlayer. Alubricant 1111 is applied onto a surface of the overcoat 111. The mediumof this embodiment is equivalent to one obtained by forming the overcoat111 after the magnetic layer 112 is formed and the grooves 11 are filledwith the non-magnetic material 118 in the discrete track medium ofEmbodiment 1 shown in FIGS. 1 and 2. Alternatively, the medium of thisembodiment is equivalent to one obtained by forming the overcoat 111after the magnetic layer 112 is formed and the grooves 21 are filledwith the non-magnetic material 118 in the patterned medium of Embodiment2 shown in FIGS. 3 and 4.

FIG. 6 is a schematic cross-sectional view of a magnetic recordingmedium according to Embodiment 4 of the present invention. A magneticrecording medium 1 or 2 of this embodiment has grooves 11 and lands 12or has grooves 21 and patterns 22. The lands 12 or the patterns 22 areformed of an overcoat 111 and a magnetic layer 112. A lubricant 1111 isapplied onto a surface of the overcoat 111. In the case of a discretetrack medium, the lands 12 form tracks. Meanwhile, in the case of apatterned medium, the patterns form respective recording bits.

FIG. 7 is a schematic cross-sectional view of a magnetic recordingmedium according to Embodiment 5 of the present invention. A magneticrecording medium 1 or 2 of this embodiment has grooves 11 and lands 12or has grooves 21 and patterns 22. The lands 12 or the patterns 22 areformed of an overcoat 111 and a magnetic layer 112. The grooves 11 orthe grooves 21 are formed of the overcoat 111 and a non-magneticmaterial 118. A lubricant 1111 is applied onto a surface of the overcoat111. In the case of a discrete track medium, the lands 12 form tracks.Meanwhile, in the case of a patterned medium, the patterns formrespective recording bits.

FIG. 8 is a schematic view of a magnetic recording medium according toEmbodiment 6 of the present invention. A magnetic recording medium 1 or2 is divided into at least three regions A to C in a radial direction. Aheight δc of cylindrical shelly land and a curvature Rc of cylindricalshelly land or a height δ of spherical shelly land and a curvature R ofspherical shelly land vary between the respective regions. Furthermore,the height δc of cylindrical shelly land or the height δ of sphericalshelly land is smallest in the middle region B with a small absolutevalue of δ yaw angle. Meanwhile, the height δc of cylindrical shellyland or the height δ of spherical shelly land in the innermost andoutermost regions A and C where the absolute value of the yaw angle isincreased is larger than that in the middle region. For example, theheight δc of cylindrical shelly land or the height δ of spherical shellyland in each of the regions A and C is 5 nm, and the height δc ofcylindrical shelly land or the height δ of spherical shelly land in theregion B is 30 nm.

With reference to FIGS. 9 to 14, description will be given of effectsachieved by the magnetic recording media of the present invention.

FIG. 9 is a schematic view of magnetic flux vectors when a magneticfield is applied to a conventional discrete track medium on its middleperipheral area with a yaw angle of 0° by a writer. In the case ofrecording on the conventional discrete track medium by applying themagnetic field by use of a writer 3, since a the track width of thewriter 3 Tww is larger than the land width Lwc, magnetic fluxes areconcentrated on the land and also leaked to adjacent tracks from sidesof the writer 3. When the magnetic fluxes are leaked to the adjacenttracks, information written into the medium is deleted. FIG. 10 is aschematic view of magnetic flux vectors when a magnetic field is appliedby the writer to the conventional discrete track medium on its innermostand outermost where the absolute value of the yaw angle is increased. Inthe innermost and outermost regions where the absolute value of the yawangle is increased, the magnetic fluxes are more easily leaked since thewriter comes closer to the adjacent track as compared with the middleregion where the yaw angle is 0°.

FIGS. 11 and 14 are views showing comparison of a distance from themagnetic layer 112 in the magnetic recording medium to the writer 3between the discrete track medium of the present invention having thecurved magnetic layer 112 and the conventional discrete track mediumhaving a flat magnetic layer. FIGS. 11A and 11B are views showingcomparison between the discrete track medium of the present invention inwhich the height δc of cylindrical shelly land is 5 nm and theconventional discrete track medium. Moreover, FIGS. 14A and 14B areviews showing comparison between the discrete track medium of thepresent invention in which the height δc of cylindrical shelly land is30 nm and the conventional discrete track medium. In FIGS. 11 and 14, L1is a distance between the magnetic layer of the adjacent track in theconventional discrete track medium and the writer 3, and L2 is adistance between the magnetic layer of the adjacent track in thediscrete track medium of the present invention and the writer 3.

FIGS. 12 and 13 are schematic views showing a configuration of amagnetic head. The magnetic head includes the writer 3, a reader 31 ofthe magnetic head, a lower magnetic pole 301, a coil 302, an uppershield 311, a lower shield 312, electrode patterns 313 and a base 314.

As shown in FIGS. 11 and 14, the distance between the magnetic layer ofthe adjacent track and the writer 3 is larger in the discrete trackmedium according to Embodiment 1 of the present invention than in theconventional discrete track medium having the flat magnetic layer. Sincemagnetic field strength is reduced in inverse proportion to the distancesquared, the magnetic fluxes are less likely to be leaked to theadjacent tracks in the discrete track medium according to Embodiment 1of the present invention as compared with the conventional discretetrack medium. Furthermore, in the discrete track medium according toEmbodiment 1 of the present invention, the larger the height ofcylindrical shelly land is, the less likely the magnetic fluxes are tobe leaked to the adjacent tracks. Thus, it is required to increase theheight δc of cylindrical shelly land towards the innermost or theoutermost. The same effect is achieved in the case of the patternedmedium according to Embodiment 2 of the present invention shown in FIGS.3 and 4. A range of the height δc of cylindrical shelly land and theheight δ of spherical shelly land in the magnetic recording mediaaccording to Embodiments 1 and 2 of the present invention is from 5 nmapproximately equivalent to the thickness of the overcoat at which aneffect of reducing meniscus adsorption starts to emerge to 30 nmrequired not to increase a magnetic spacing.

FIGS. 15A and 15B are views showing comparison of a magnetic spacing hmand a flying height hf at a position of the reader and writer in themagnetic head between the discrete track medium of the present inventionhaving the curved magnetic layer and the conventional discrete trackmedium having the flat magnetic layer as well as the curved overcoat.The magnetic spacing hm, in the case of reproduction by use of aperpendicular magnetic recording system or in the case of recording andreproduction by use of a longitudinal magnetic recording system, is adistance from the surface of the magnetic layer 112 to the reader 31 inthe magnetic head or to the writer 3. The magnetic spacing hm in thecase of recording by use of the perpendicular magnetic recording systemis a distance from the surface of the underlayer 1113 such as the softmagnetic underlayer to the writer 3. FIG. 15A shows the case ofreproduction by use of the perpendicular magnetic recording system orthe case of recording and reproduction by use of the longitudinalmagnetic recording system. Meanwhile, FIG. 15B shows the case ofrecording by use of the perpendicular magnetic recording system.

As shown in FIGS. 15A and 15B, the magnetic spacing hm is smaller in thecase of the magnetic recording medium according to Embodiment 1 of thepresent invention than in the case of the conventional discrete trackmedium, when both the recording media have the same cylindrical shellyland shape and the same flying height hf at a position of a reader andwriter in a magnetic head slider, which is related to durability of amagnetic disk apparatus. For example, in both of the discrete trackmedium according to Embodiment 1 of the present invention and theconventional discrete track medium, the thickness of the overcoat 111 isset to 5 nm, the thickness of the magnetic layer 112 is set to 32 nm andthe height δc of cylindrical shelly land is set to 30 nm. In this case,when the flying height hf at the position of the reader and writer isset the same, a center portion of the overcoat is required to have athickness of 35 nm in order to set the height δc of cylindrical shellyland in the conventional discrete track medium to 30 nm. Thus, themagnetic spacing hm is increased by 30 nm that is the height δc ofcylindrical shelly land. Since magnetic field strength is reduced ininverse proportion to the magnetic spacing squared, it is found out thatthe discrete track medium according to Embodiment 1 of the presentinvention having a small magnetic spacing has a higher areal density.

With reference to FIG. 15C, description will be given of a range of theheight δc of cylindrical shelly land in the discrete track mediumaccording to Embodiment 1 of the present invention for preventing anincrease in the magnetic spacing. Here, it is assumed that a distancefrom the end of the writer 3 to a center position of the underlayer 1113such as the soft magnetic underlayer is a magnetic spacing hm1 and adistance from the end of the writer 3 to an end of the underlayer 1113such as the soft magnetic underlayer is a magnetic spacing hm2. In thiscase, since the magnetic field strength is reduced in inverse proportionto the magnetic spacing squared, conditions expressed by the followingformulas (1) to (3) are required so that all magnetic fluxes generatedfrom the writer 3 in recording are concentrated on the center positionof the underlayer 1113 such as the soft magnetic underlayer withoutreaching the end of the underlayer 1113 such as the soft magneticunderlayer.

$\begin{matrix}{h_{m\; 1} > h_{m\; 2}} & (1) \\{h_{m\; 1} = \sqrt{\left( \frac{L_{wc}}{2} \right)^{2} + \left( {h_{f} + t_{c} + t_{mag}} \right)^{2}}} & (2) \\{h_{m\; 2} = {h_{f} + t_{c} + t_{mag} + \delta_{c}}} & (3)\end{matrix}$

Here, Lwc is the land width and the track width of the writer 3, tc isthe thickness of the overcoat 111, and tmag is the thickness of themagnetic layer 112. The following formula (4) is obtained by solving theformulas (1) to (3).

$\begin{matrix}{\delta_{c} < {{- \left( {h_{f} + t_{c} + t_{mag}} \right)} + \sqrt{\left( {h_{f} + t_{c} + t_{mag}} \right)^{2} + \left( \frac{L_{wc}}{2} \right)^{2}}}} & (4)\end{matrix}$

Accordingly, the range of the height δc of cylindrical shelly land inthe discrete track medium according to Embodiment 1 of the presentinvention for preventing an increase in the magnetic spacing is obtainedby the formula (4). For example, in the case where Lwc=100 nm, tc=5 n,tmag=15 nm and hf=5 nm, the range of the height δc of cylindrical shellyland in the discrete track medium according to Embodiment 1 of thepresent invention for preventing an increase in the magnetic spacing isset to 30 nm or less.

Although, here, the discrete track medium has been described, the samegoes for the patterned medium of the present invention having the curvedmagnetic layer and the patterned medium having the flat magnetic layeras well as the curved overcoat.

With reference to FIGS. 16 to 18, description will be given of anothereffect achieved by the magnetic recording media of the presentinvention.

FIG. 16A is a schematic cross-sectional view when the discrete trackmedium 1 or the patterned medium 2 according to the present inventioncomes into contact with a magnetic head slider 4. FIG. 16B is aschematic cross-sectional view when a conventional discrete track medium10 or a conventional patterned medium 20 comes into contact with themagnetic head slider 4. The lubricant 1111 is applied onto a surface ofeach of the media.

A meniscus adsorptive force Fmc of the lubricant is generated when themagnetic head slider and the discrete track medium come into contactwith each other. Meanwhile, a meniscus adsorptive force Fm of thelubricant is generated when the magnetic head slider and the patternedmedium come into contact with each other. The meniscus adsorptive forcesFmc and Fm are expressed by Fmc=8πγRc and Fm=47πγR, respectively. γ is asurface energy of the lubricant, and γ=0.022 N/m in the case of alubricant Z-dol. The curvature Rc of cylindrical shelly land isexpressed by Rc=((Lwc/2)²+δc²)/(2δc) by use of the land width Lwc andthe height δc of cylindrical shelly land. The curvature R of sphericalshelly land is expressed by R=((Lw/2)²+δ²)/(2δ) by use of the patternwidth Lw and the height δ of spherical shelly land.

FIG. 17A shows calculation results on a relationship between themeniscus adsorptive force Fmc and the curvature Rc of cylindrical shellyland by use of the equation described above when the lubricant Z-dol(γ=0.022 N/m) is used. Moreover, FIG. 17B shows calculation results on arelationship between the meniscus adsorptive force Fmc and the height δcof cylindrical shelly land by use of the equation described above whenthe lubricant Z-dol (γ=0.022 N/m) is used. It is found out from thesegraphs that the smaller the curvature Rc of cylindrical shelly land andthe larger the height δc of cylindrical shelly land, the smaller themeniscus adsorptive force Fmc becomes. In the case of the magneticrecording medium (Lwc=100 nm and δc=5 nm) of Embodiment 1, the meniscusadsorptive force Fmc is set to 0.00014 mN. In the case of theconventional magnetic recording medium in which Rc=∞, the meniscusadsorptive force Fmc becomes infinite. Accordingly, since the magneticrecording medium of Embodiment 1 comes into contact with the slider onits cylindrical shelly lands having a large height, the meniscusadsorptive force is reduced as compared with the conventional discretetrack medium. Thus, slider vibration due to an adsorption phenomenonwith the medium can be reduced, and a flying height of the slider can bereduced.

FIG. 18A shows calculation results on a relationship between themeniscus adsorptive force Fm and the curvature R of spherical shellyland by use of the equation described above when the lubricant Z-dol(γ=0.022 N/m) is used. Moreover, FIG. 18B shows calculation results on arelationship between the meniscus adsorptive force Fm and the height δof spherical shelly land by use of the equation described above when thelubricant Z-dol (γ=0.022 N/m) is used. It is found out from these graphsthat the smaller the curvature R of spherical shelly land and the largerthe height δ of spherical shelly land, the smaller the meniscusadsorptive force Fm becomes. In the case of the magnetic recordingmedium of Embodiment 2, the meniscus adsorptive force Fm is reduced to0.00007 mN. In the case of the conventional magnetic recording medium inwhich R=∞, the meniscus adsorptive force Fm also becomes infinite.Accordingly, since the magnetic recording medium of Embodiment 2 comesinto contact with the slider on its spherical shelly lands having alarge height, the meniscus adsorptive force is reduced as compared withthe conventional patterned medium. Thus, slider vibration due to anadsorption phenomenon with the medium can be reduced, and a flyingheight of the slider can be reduced.

Particularly, it is found out from FIGS. 18A and 18B that, when theheight δc of cylindrical shelly land is set to 5 nm or less or when theheight δ of spherical shelly land is set to 5 nm or less, the effect ofreducing the meniscus adsorptive force significantly emerges and both ofFmc and Fm are set to 0.0006 mN or less.

In order to prevent adsorption of the flying slider on the mediumsurface even if the meniscus adsorptive force Fm is generated when theflying slider comes close to the lubricant on the medium surface, it isrequired to set the meniscus adsorptive force Fm to be significantlysmaller than an air-bearing force of the flying slider. A currently usedsuspension preload is about 10 to 30 mN. The air-bearing force of theflying slider is also approximately the same as the suspension preload.When the height δc of cylindrical shelly land is set to 5 nm or less, aneffect of significantly reducing the meniscus adsorptive force Fm to0.006% or less as compared with the air-bearing force of 10 mN isachieved. Thus, the range of the height δc of cylindrical shelly land isset to 5 nm or less.

With reference to FIGS. 19A to 19F, description will be given of amethod for manufacturing the magnetic recording media according toEmbodiments 1 and 2 of the present invention. FIGS. 19A to 19F show themethod for manufacturing the discrete track medium of Embodiment 1having the lands and the grooves. Meanwhile, in the case ofmanufacturing the patterned medium of Embodiment 2, the patterns whichform the respective recording bits are formed instead of the lands whichform the tracks.

(a) An underlayer 113 such as SiO₂ is formed by spin coating on anon-magnetic substrate 114. Thereafter, a resist 115 is formed by spincoating on the underlayer 113 such as SiO₂.

(b) By use of an electron beam lithography method or a photolithographymethod, the resist 115 is formed into a predetermined shape of lands orgrooves.

(c) The non-magnetic substrate 114 having the resist 115 formed thereonis placed on a hot plate 117 heated to about 120 to 180° C. for about 15to 60 minutes.

(d) When the resist 115 is remelted, a surface tension thereof allowsthe lands or the grooves to be formed into a predetermined cylindricalshelly shape or spherical shelly shape.

(e) The resist 115 having the cylindrical shelly or spherical shellylands or grooves is subjected to sputtering by use of a reactive ionsputtering method to form the underlayer 113 such as SiO₂ into thecylindrical shelly or spherical shelly shape.

(f) An underlayer 1113 such as a soft magnetic underlayer, a magneticlayer 112, an overcoat 111 and a lubricant 1111 are formed on theunderlayer 113 such as SiO₂ having the cylindrical shelly or sphericalshelly lands or grooves by sputtering using the reactive ion sputteringmethod.

With reference to FIGS. 20A to 20D, description will be given of anothermethod for manufacturing the magnetic recording media according toEmbodiments 1 and 2 of the present invention. FIGS. 20A to 20D show themethod for manufacturing the discrete track medium of Embodiment 1having the lands and the grooves. Meanwhile, in the case ofmanufacturing the patterned medium of Embodiment 2, the patterns whichform the respective recording bits are formed instead of the lands whichform the tracks.

(a) An underlayer 113 such as SiO₂ is formed by spin coating on anon-magnetic substrate 114. Thereafter, a resist 115 is formed by spincoating on the underlayer 113 such as SiO₂.

(b) By use of the electron beam lithography method or thephotolithography method, the resist 115 is formed into cylindricalshelly or spherical shelly lands or grooves by extending exposure timeor developing time.

(c) The resist 115 having the cylindrical shelly or spherical shellylands or grooves is subjected to sputtering by use of the reactive ionsputtering method to form the underlayer 113 such as SiO₂ into thecylindrical shelly or spherical shelly shape.

(d) An underlayer 1113 such as a soft magnetic underlayer, a magneticlayer 112, an overcoat 111 and a lubricant 1111 are formed on theunderlayer 113 such as SiO₂ having the cylindrical shelly or sphericalshelly lands or grooves by sputtering using the reactive ion sputteringmethod.

With reference to FIGS. 21A to 21H, description will be given of anothermethod for manufacturing the magnetic recording media according toEmbodiments 1 and 2 of the present invention. FIGS. 21A to 21H show themethod for manufacturing the discrete track medium of Embodiment 1having the lands and the grooves. Meanwhile, in the case ofmanufacturing the patterned medium of Embodiment 2, the patterns whichform the respective recording bits are formed instead of the lands whichform the tracks.

(a) An underlayer 113 such as SiO₂ is formed by spin coating on anon-magnetic substrate 114. Thereafter, a resist 115 is formed by spincoating on the underlayer 113 such as SiO₂.

(b), (c) and (d) By use of a nanoimprint method, pressure is applied onthe resist 115 by a mold 116 to form the resist 115 into a predeterminedshape of lands or grooves.

(e) The non-magnetic substrate 114 having the resist 115 formed thereonis placed on a hot plate 117 heated to about 120 to 180° C. for about 15to 60 minutes.

(f) When the resist 115 is remelted, a surface tension thereof allowsthe lands or the grooves to be formed into a predetermined cylindricalshelly shape or spherical shelly shape.

(g) The resist 115 having the cylindrical shelly or spherical shellylands or grooves is subjected to sputtering by use of the reactive ionsputtering method to form the underlayer 113 such as SiO₂ into thecylindrical shelly or spherical shelly shape.

(h) An underlayer 1113 such as a soft magnetic underlayer, a magneticlayer 112, an overcoat 111 and a lubricant 1111 are formed on theunderlayer 113 such as SiO₂ having the cylindrical shelly or sphericalshelly lands or grooves by sputtering using the reactive ion sputteringmethod.

With reference to FIGS. 22A to 22F, description will be given of anothermethod for manufacturing the magnetic recording media according toEmbodiments 1 and 2 of the present invention. FIGS. 22A to 22F show themethod for manufacturing the discrete track medium of Embodiment 1having the lands and the grooves. Meanwhile, in the case ofmanufacturing the patterned medium of Embodiment 2, the patterns whichform the respective recording bits are formed instead of the lands whichform the tracks.

(a) An underlayer 113 such as SiO₂ is formed by spin coating on anon-magnetic substrate 114. Thereafter, a resist 115 is formed by spincoating on the underlayer 113 such as SiO₂.

(b), (c) and (d) By use of the nanoimprint method, pressure is appliedon the resist 115 by a mold 116 having a predetermined cylindricalshelly or spherical shelly shape to form the resist 115 into lands orgrooves having a predetermined cylindrical shelly or spherical shellyshape.

(e) The resist 115 having the cylindrical shelly or spherical shellylands or grooves is subjected to sputtering by use of the reactive ionsputtering method to form the underlayer 113 such as SiO₂ into thecylindrical shelly or spherical shelly shape.

(f) An underlayer 1113 such as a soft magnetic underlayer, a magneticlayer 112, an overcoat 111 and a lubricant 1111 are formed on theunderlayer 113 such as SiO₂ having the cylindrical shelly or sphericalshelly lands or grooves by sputtering using the reactive ion sputteringmethod.

With reference to FIGS. 23A to 23E, description will be given of amethod for manufacturing a cylindrical shelly or spherical shelly mold116 for the magnetic recording media according to Embodiments 1 and 2 ofthe present invention. FIGS. 23A to 23E show the method formanufacturing the discrete track medium of Embodiment 1 having the landsand the grooves. Meanwhile, in the case of manufacturing the patternedmedium of Embodiment 2, the patterns which form the respective recordingbits are formed instead of the lands which form the tracks.

(a) An underlayer 113 such as SiO₂ is formed by spin coating on anon-magnetic substrate 114. Thereafter, a resist 115 is formed by spincoating on the underlayer 113 such as SiO₂. As a material of thenon-magnetic substrate 114, quartz or the like is used in the case of anoptical imprint method and a silicon substrate or the like is used inthe case of a thermal imprint method.

(b) By use of the electron beam lithography method or thephotolithography method, the resist 115 is formed into a predeterminedshape of lands or grooves.

(c) The non-magnetic substrate 114 having the resist 115 formed thereonis placed on a hot plate 117 heated to about 120 to 180° C. for about 15to 60 minutes.

(d) When the resist 115 is remelted, a surface tension thereof allowsthe lands or the grooves to be formed into a predetermined cylindricalshelly shape or spherical shelly shape.

(e) The resist 115 having the cylindrical shelly or spherical shellylands or grooves is subjected to sputtering by use of the reactive ionsputtering method to form the underlayer 113 such as SiO₂ into thecylindrical shelly or spherical shelly shape. The non-magnetic substrate114 having the cylindrical shelly or spherical shelly underlayer 113such as SiO₂ is used as a mold 116 having a cylindrical shelly orspherical shelly shape.

With reference to FIGS. 24A to 24I, description will be given of amethod for manufacturing the magnetic recording medium according toEmbodiment 3 of the present invention.

(a) An underlayer 113 such as SiO₂ is formed by spin coating on anon-magnetic substrate 114. Thereafter, a resist 115 is formed by spincoating on the underlayer 113 such as SiO₂.

(b) By use of the electron beam lithography method or thephotolithography method, the resist 115 is formed into a predeterminedshape of lands or grooves.

(c) The non-magnetic substrate 114 having the resist 115 formed thereonis placed on a hot plate 117 heated to about 120 to 180° C. for about 15to 60 minutes.

(d) When the resist 115 is remelted, a surface tension thereof allowsthe lands or the grooves to be formed into a predetermined cylindricalshelly shape or spherical shelly shape.

(e) The resist 115 having the cylindrical shelly or spherical shellylands or grooves is subjected to sputtering by use of the reactive ionsputtering method to form the underlayer 113 into the cylindrical shellyor spherical shelly shape.

(f) An underlayer 1113 such as a soft magnetic underlayer and a magneticlayer 112 are formed on the underlayer 113 such as SiO₂ having thecylindrical shelly or spherical shelly lands or grooves.

(g) The magnetic layer 112 having the cylindrical shelly or sphericalshelly lands or grooves is subjected to sputtering by use of thereactive ion sputtering method to fill the grooves with a non-magneticmaterial 118 such as SiO₂.

(h) By use of an ion etching method, the non-magnetic material 118 isremoved until the magnetic layer 112 is exposed.

(i) An overcoat 111 and a lubricant 1111 are formed on the non-magneticmaterial 118 and the exposed magnetic layer 112 by sputtering using thereactive ion sputtering method.

With reference to FIGS. 25A to 25C, description will be given of amethod for manufacturing the magnetic recording medium according toEmbodiment 6 of the present invention.

(a) When the non-magnetic substrate 114 having the resist 115 formedthereon is placed on the hot plate 117 as shown in FIG. 19C, a ring-likehot plate 117 that can transmit heat to an outer peripheral portion C ofthe medium is used to form cylindrical shelly or spherical shelly landsor grooves specific to the outer peripheral portion C.

(b) Similarly, a ring-like hot plate 117 that can transmit heat to amiddle peripheral portion B of the medium is used to form cylindricalshelly or spherical shelly lands or grooves specific to the middleperipheral portion B of the medium.

(c) Similarly, a ring-like hot plate 117 that can transmit heat to aninner peripheral portion A of the medium is used to form cylindricalshelly or spherical shelly lands or grooves specific to the innerperipheral portion A of the medium. As described above, a heatingtemperature and a heating time can be changed with respect to radialpositions on the medium. Thus, it is possible to form lands or groovesvarying in shape, such as a cylindrical shape or a spherical shape, withrespect to the radial positions on the medium.

Here, the method for manufacturing the discrete track medium has beendescribed above. However, the patterned medium of the present inventionhaving the curved magnetic layer can also be manufactured by use of thesame method.

With reference to FIG. 26, description will be given of a range of theheight δc of cylindrical shelly land of the discrete track mediumaccording to Embodiments 4 and 5 of the present invention. The mediumaccording to Embodiments 4 and 5 of the present invention is a magneticrecording medium in which a magnetic layer provided in the lands has acurved upper surface that is convex in a medium surface direction and aflat lower surface.

As shown in FIG. 26, in the case of recording on the discrete trackmedium by using the writer 3 to apply a magnetic field thereto,conditions expressed by the following formulas (5) to (12) are requiredto make magnetic fluxes less likely to be leaked to adjacent tracks inthe discrete track medium according to Embodiments 4 and 5 of thepresent invention as compared with the conventional discrete trackmedium. Accordingly, the range of the height δc of cylindrical shellyland takes a value that satisfies the formulas (5) to (12).Specifically, required is a condition that a difference (bb−aa) betweena distance bb from the magnetic layer of the adjacent track in thediscrete track medium of the present invention to the writer and adistance aa from the magnetic layer to the writer is larger than adifference (b−a) between a distance b from the magnetic layer of theadjacent track in the conventional discrete track medium to the writerand a distance a from the magnetic layer to the writer.

$\begin{matrix}{{{bb} - {aa}} > {b - a}} & (5) \\{{bb} = \sqrt{\left( {\frac{L_{wc}}{2} - x + G_{wc}} \right)^{2} + \left( {h_{m\; 3} + y} \right)^{2}}} & (6) \\{{aa} = {h_{m\; 3} + y}} & (7) \\{b = \sqrt{G_{wc}^{2} + h_{m\; 3}^{2}}} & (8) \\{a = h_{m\; 3}} & (9) \\{h_{m\; 3} = {h_{f} + t_{c} + t_{L}}} & (10) \\{y = {{\delta_{c}\left( \frac{2}{L_{w}} \right)}^{2}x^{2}}} & (11) \\{\delta_{c} = {R_{c} - \sqrt{R_{c}^{2} - \left( \frac{L_{wc}}{2} \right)^{2}}}} & (12)\end{matrix}$

Here, (x, y) is a position of the magnetic layer of the adjacent trackin the discrete track medium of the present invention, and t_(L) is athickness of the lubricant 1111.

For example, in the case where Lwc=100 nm, Gwc=Lwc/2=50 nm, Rc=57 nm,tc=5 nm, t_(L)=2 nm, hf=25 nm, hm3=32 nm, x=40 nm, y=18.96 nm, andδc=29.63 nm, bb−aa=27.8 nm and b−a=27.36 nm are established and thus theformula (5) is satisfied. Accordingly, it is found out that, when theheight δc of cylindrical shelly land in the discrete track mediumaccording to Embodiments 4 and 5 of the present invention is 29.63 nm,the magnetic fluxes are less likely to be leaked to the adjacent tracksas compared with the conventional discrete track medium.

FIGS. 27A and 27B show an embodiment of a magnetic disk apparatusaccording to the present invention. FIG. 27A is a schematic plan viewand FIG. 27B is a schematic side view showing a state where a magnetichead slider 4 performs scan and seek operations while flying above thesurface of the magnetic recording medium 1 or 2. A magnetic diskapparatus 5 includes the magnetic recording medium 1 or 2 according toEmbodiment 1 or 2 of the present invention, a drive member 6 whichrotates the medium, the magnetic head slider 4, a support 7 of themagnetic head slider 4, a supporting arm 8 for positioning, a drivemember 9 for the supporting arm, and a circuit 99 for processing arecording and reproducing signal of a magnetic head mounted on themagnetic head slider 4.

1. A magnetic recording medium comprising: lands which have a magneticlayer and form recording tracks; and grooves formed between the landsadjacent to each other, wherein an upper surface of the magnetic layerprovided in the lands has a curved shape that is convex in a mediumsurface direction.
 2. The magnetic recording medium according to claim1, wherein a thickness of the magnetic layer provided in the lands isapproximately uniform in a track width direction.
 3. The magneticrecording medium according to claim 1, wherein upper and lower surfacesof the magnetic layer when viewed from a track width direction have acurved shape that is convex upward.
 4. The magnetic recording mediumaccording to claim 1, wherein an overcoat is provided on the magneticlayer, and when a thickness of the magnetic layer is set to tmag, athickness of the overcoat is set to tc, a track width of a writer is setto Lw, a flying height of a magnetic head is set to hf, and a lengthfrom a position where the curved shape of the upper surface of themagnetic layer starts to a top of the curved shape is set to be a landheight δ, the following formula is satisfied.$\delta < {{- \left( {h_{f} + t_{c} + t_{mag}} \right)} + \sqrt{\left( {h_{f} + t_{c} + t_{mag}} \right)^{2} + \left( \frac{L_{w}}{2} \right)^{2}}}$5. The magnetic recording medium according to claim 1, wherein, when alength from a position where the curved shape of the upper surface ofthe magnetic layer starts to a top of the curved shape is set to be aland height, the land height is not less than 5 nm and not more than 30nm.
 6. The magnetic recording medium according to claim 5, wherein theland height is higher in inner and outer peripheral regions than in aregion sandwiched between the inner and outer peripheral regions.
 7. Themagnetic recording medium according to claim 1, wherein the grooves arefilled with a non-magnetic material.
 8. The magnetic recording mediumaccording to claim 1, wherein a lower surface of the magnetic layer hasa curved shape that is convex in the medium surface direction.
 9. Amagnetic recording medium comprising: a plurality of bit patterns whichhave a magnetic layer and are arranged in isolation from theirsurrounding along a crosstrack direction, wherein an upper surface ofthe magnetic layer provided in the bit patterns has a curved shape thatis convex in a medium surface direction.
 10. The magnetic recordingmedium according to claim 9, wherein a thickness of the magnetic layerprovided in the bit patterns is approximately uniform in the crosstrackdirection and in a track width direction.
 11. The magnetic recordingmedium according to claim 9, wherein the magnetic layer provided in thebit patterns has a spherical shelly shape.
 12. The magnetic recordingmedium according to claim 9, wherein an overcoat is provided on themagnetic layer, and when a thickness of the magnetic layer is set totmag, a thickness of the overcoat is set to tc, a track width of awriter is set to Lw, a flying height of a magnetic head is set to hf,and a length from a position where the curved shape of the upper surfaceof the magnetic layer starts to a top of the curved shape is set to be aland height δ, the following formula is satisfied.$\delta < {{- \left( {h_{f} + t_{c} + t_{mag}} \right)} + \sqrt{\left( {h_{f} + t_{c} + t_{mag}} \right)^{2} + \left( \frac{L_{wc}}{2} \right)^{2}}}$13. The magnetic recording medium according to claim 9, wherein, when alength from a position where the curved shape of the upper surface ofthe magnetic layer starts to a top of the curved shape is set to be aland height, the land height is not less than 5 nm and not more than 30nm.
 14. The magnetic recording medium according to claim 13, wherein theland height is higher in inner and outer peripheral regions than in aregion sandwiched between the inner and outer peripheral regions. 15.The magnetic recording medium according to claim 9, wherein anon-magnetic material is provided between the plurality of bit patternsarranged in isolation.
 16. The magnetic recording medium according toclaim 9, wherein a lower surface of the magnetic layer has a curvedshape that is convex in the medium surface direction.
 17. A magneticrecording and reproducing apparatus comprising: a magnetic recordingmedium; a medium drive member which drives the magnetic recordingmedium; a magnetic head which performs recording and reproductionoperations on the magnetic recording medium; and a magnetic head drivemember which positions the magnetic head with respect to the magneticrecording medium, wherein the magnetic recording medium includes landswhich have a magnetic layer and form recording tracks, and groovesformed between the lands adjacent to each other, and an upper surface ofthe magnetic layer provided in the lands has a curved shape that isconvex in a medium surface direction.
 18. The magnetic recording andreproducing apparatus according to claim 17, wherein a thickness of themagnetic layer provided in the lands is approximately uniform in a trackwidth direction.
 19. The magnetic recording and reproducing apparatusaccording to claim 17, wherein upper and lower surfaces of the magneticlayer when viewed from a track width direction have a curved shape thatis convex upward.
 20. The magnetic recording and reproducing apparatusaccording to claim 17, wherein the magnetic recording medium has anovercoat on the magnetic layer, and when a thickness of the magneticlayer is set to tmag, a thickness of the overcoat is set to tc, a trackwidth of a writer of the magnetic head is set to Lw, a flying height ofthe magnetic head is set to hf, and a length from a position where thecurved shape of the upper surface of the magnetic layer starts to a topof the curved shape is set to be a land height δ, the following formulais satisfied.$\delta < {{- \left( {h_{f} + t_{c} + t_{mag}} \right)} + \sqrt{\left( {h_{f} + t_{c} + t_{mag}} \right)^{2} + \left( \frac{L_{wc}}{2} \right)^{2}}}$